WASHINGTON — Democratic Sen. Robert Menendez of New Jersey denied Wednesday that he accepted free plane trips and contact with prostitutes from a Florida eye doctor whose offices were raided by federal agents Tuesday night.

The raid, reported by The Miami Herald, targeted Salomon Melgen, a physician described by the newspaper as a prominent campaign donor to Menendez and other Democrats. The Herald said Melgen owes $11.1 million in back taxes.

The conservative Daily Caller news website quotes anonymous sources who allege Melgen provided Menendez with prostitutes — some of them underage — at his luxury home at the Casa de Campo resort in the Dominican Republic.

"Dr. Melgen has been a friend and political supporter of Sen. Menendez for many years," the statement read. "Sen. Menendez has traveled on Dr. Melgen's plane on three occasions, all of which have been paid for and reported appropriately. Any allegations of engaging with prostitutes are manufactured by a politically motivated right-wing blog and are false."

Menendez's office did not say whether the three trips were to the Dominican Republic or elsewhere. The statement also did not say how the trips were reported or how Menendez paid for them — with his own money or through his senatorial or campaign accounts.

The Associated Press reported it found no records reporting payments to Melgen or trips aboard Melgen's plane in six years' worth of office and travel-related expenses for Menendez's Senate office, or in six years' worth of campaign expenses on file with the Federal Election Commission.

FBI Special Agent James Marshall confirmed Wednesday that "we are conducting law enforcement activity in the general vicinity" of Metrocentre Boulevard, the location of one of Melgen's offices in West Palm Beach, Fla.

Marshall declined to comment further.

According to the Herald story, the FBI investigation is believed to focus on Melgen's finances and allegations that he provided Menendez with free trips and prostitutes. Prostitution is legal in the Dominican Republic. Menendez is divorced and has two children.

A reporter for The Daily Caller asked Menendez about the allegations on Monday as a Gannett Washington Bureau reporter was interviewing the senator about an unrelated topic.

"I'm not going to respond to the fallacious allegations of your story," Menendez said.

"All anyone here has to look at is the source where this comes from," he said. "It's a source that has brought up a lot of non-issues."

The Daily Caller first published a story about the allegations last fall, prompting Samuel Thompson, chairman of the Middlesex County, N.J., Republican Organization and a New Jersey state senator, to ask the state Senate ethics committee to investigate whether Menendez had failed to report the trips on expense reports.

It's unclear whether the ethics committee, which does not comment on current investigations, is looking into the allegations.

Thompson said Wednesday that he had not heard back from the committee.

The allegations appear to have first surfaced in April, when a tipster calling himself "Peter Williams" approached the Washington-based watchdog group Citizens for Responsibility and Ethics in Washington (CREW).

CREW executive director Melanie Sloan said the group exchanged e-mails with Williams for several months in an attempt to confirm the allegations, but gave up when Williams refused to speak with the group by phone.

"We just had no way to know whether these things were true or not, but he had a lot of detail," Sloan said.

CREW forwarded the e-mails in July to the FBI, other Justice Department officials and ABC News.

On Wednesday, CREW released 56 pages of email exchanges between Williams and the group as well as a memo it sent the FBI summarizing the emails and detailing its own investigation based on them.

"While CREW has been unable to either prove or disprove that Sen. Menendez engaged in sexual conduct with underage girls in the Dominican Republic, we have been able to confirm some information provided," the group said, asking for "an immediate, thorough, and fair investigation of these allegations."

"If a top government official like Sen. Menendez – who has sworn to uphold the laws of the United States – has, in fact, engaged in the conduct alleged, he should be exposed and prosecuted to the fullest extent of the law," the group said.

Last week, e-mails that appear to have been sent between an FBI special agent, Regino Chavez, and Williams were forwarded to several media outlets. Those e-mails indicate the FBI followed up on CREW's contact with Williams, but Williams also refused to meet with FBI officials.

Chavez did not respond to a message left on his voice mail seeking comment for this story.

"I feel like we did the right thing by sending this to the FBI, but I am worried that someone may have been using us to smear a politician," Sloan said.

Sloan said she finds the timing of the allegations, which Williams told her date to 2008, suspect.

The allegations come as Menendez is about to become chairman of the powerful Senate Foreign Relations Committee. He replaces Sen. John Kerry, D-Mass., who was confirmed Tuesday as secretary of State. Menendez was re-elected last fall with 58.5% of the vote.

"There's reason to doubt the credibility of this stuff," Sloan said. "There's reason to withhold judgment until we know more."

Melgen, a registered Democrat, has made $193,350 in political contributions since 1998, including $14,200 to Menendez, according to FEC records. Menendez was chairman of the Senate Democratic Campaign Committee, which raises money for Democratic Senate candidates, from 2009 to 2011.